“Runner’s high” and other brain chemistry changes during workouts

Can swearing help me push harder in a workout?

If you’re looking for that extra edge that will allow you to lift one more rep or maintain your pace near the end of a tough workout, consider the latest research from psychologist Richard Stephens of Keele University in Britain. After hitting his thumb with a hammer, Stephens let loose with a string of expletives—a common enough occurrence, but one that left him wondering why humans have this nearly universal habit of “cathartic swearing.”

To find out, he asked 67 volunteers to dunk their hands in ice-cold water and keep them there for as long as possible. Half of them were told to yell a word from their list of “five words you might use after hitting yourself on the thumb with a hammer,” while the other half chose a word from their list of “five words to describe a table.” Sure enough, swearing significantly increased the length of time subjects could withstand the pain, by 30 percent for men and 44 percent for women—a difference that may have something to do with the fact that women swear less often, Stephens speculates. Swearing also raised heart rates and decreased perceived pain, again with a greater effect in women than men.

The results were actually the opposite of what Stephens expected. Pain theorists had believed that swearing was a form of “catastrophizing” or exaggerating the severity of the pain, but Stephens’s results, which appeared in 2009 in the journal NeuroReport, suggest that something else is happening. Instead, it may be that swearing triggers feelings of aggression that allow us to tap into our fight-or-flight mechanism, pumping adrenaline through our veins and blocking pain. Similarly, Stephens points out, sports coaches often psych their players up with pre-game speeches laden with profanity. Whatever the precise mechanism, the finding that swearing increases pain tolerance explains why evolution has ensured that the behavior survives in virtually all cultures. Most language is generated in the left brain, but swearing appears to arise in the older emotion centers of the right brain: the limbic system and the basal ganglia. So the next time you’re trying to get through the painful part of a race or workout, remember that you have the code words to access this primitive part of your brain—as long as there aren’t any children within earshot.

(Strangely, this isn’t the only study to suggest that expressing your inner jerk can boost your physical performance. In 2010, Harvard University psychologists reported that doing a good deed like giving money to charity, or even imagining doing a good deed, enabled volunteers to hold up a five-pound weight for longer than they could when thinking neutral thoughts. But they gained even greater strength from imagining themselves doing evil deeds like harming someone else—even without swearing!)

Is there such a thing as “runner’s high”?

For decades, the “runner’s high” was the Yeti of exercise science: an exciting phenomenon that lots of people claimed to have seen but that couldn’t be reproduced on demand and couldn’t be reliably documented or measured. The lucky ones described feelings of exaltation, effortlessness, and intense euphoria, usually during or after long or difficult runs, and some attributed it to the mood-altering effects of brain chemicals called endorphins. But skeptics weren’t convinced: University of Michigan researcher Huda Akil, the president of the Society for Neuroscience, dismissed the idea as “a total fantasy in the pop culture” in a 2002 interview with the New York Times.

Endorphins are endogenous morphines, chemicals produced naturally within the body that alter mood and block pain much like opiate drugs such as morphine. Researchers have known for decades that vigorous exercise raises endorphin levels in the blood, but the brain is almost completely isolated from the blood in the rest of your body by a “blood-brain barrier.” It was only in 2008 that researchers at the University of Munich, using new techniques, were able to perform a direct test of endorphin levels in the brains of runners who had just completed a two-hour run. Sure enough, endorphins were released in the brains of the exhausted runners—and more importantly, there was a direct correlation between the level of endorphin activity and the level of euphoria reported by the runners (who didn’t know what the study was trying to measure). The areas of the brain most affected were the limbic and prefrontal areas, which are associated with mood.

Endorphin, pain tolerance, adrenaline, “Runner’s high” ,

Despite its fame, runner’s high is actually quite rare, at least in its most extreme euphoric form. But some researchers believe that post-exercise endorphins have subtler effects that are far more widespread than previously realized—and that the opioid rush explains why some people become effectively addicted to exercise, persisting in their daily ritual even when they’re injured or unhealthy. In support of this theory, psychologists at Tufts University administered naxolone, which blocks the action of opioid drugs, to a group of rats who were accustomed to vigorous exercise. The rats displayed symptoms of withdrawal, including teeth chattering and “wet dog shakes”—exactly as morphine-addicted rats would have under the same circumstances.

Of course, most people manage to find a happy medium: they may not experience the euphoric thrills of runner’s high, but neither are they desperately jonesing for their next hit of exercise. Instead, the endorphins produced during their workout contribute to the general sense of calm and well-being that typically follows exercise—and that’s enough to keep them coming back for more.

Will taking a fitness class or joining a team change my brain chemistry during workouts?

Consider the similarities between a modern exercise class and an ancient religious rite—the wise leader guiding the group through a series of ritualized movements, in perfect synchronization. If you’re struggling to keep faith with your fitness goals, this apparent coincidence might offer a solution. New research suggests that group exercise unleashes a flood of chemicals in the brain, triggering the same responses that have made collective activities from dancing and laughter to religion itself such enduring aspects of human culture. For some (but not all) people, finding workout buddies could help turn fitness into a pleasant addiction.

In a 2010 issue of Biology Letters, researchers from Oxford’s Institute of Cognitive and Evolutionary Anthropology reported on a study of the university’s famed rowing team. The crew was divided into teams of six, each of which performed a series of identical workouts on rowing machines. The only variable was whether the workouts were performed alone or in teams with the six rowing machines synchronized by the crew’s coxswain. After each workout, a blood-pressure cuff was tightened around one arm of each subject until he reported pain, an indirect method of measuring endorphin levels in the brain. Endorphins—the same chemicals that stimulate runner’s high—produce a mild opiate high and create a sense of well-being as well as blocking pain. Sure enough, the rowers’ pain threshold was consistently twice as high after exercising with their team-mates compared with exercising alone, even though the intensity of the workouts was identical.

So where does this magic come from? The endorphin surges can likely be traced back to the evolutionary benefits of group bonding, the researchers suggest. Earlier studies have indicated that synchronized physical activity elevates mood and is associated with greater altruism. But synchronization is probably not the only factor involved, notes lead author Emma Cohen, who is now at the Max Planck Institute for Evolutionary Anthropology in Germany. “We also suspect that shared goals—ultimate goals, like winning the big race, and proximate goals, like endeavoring to row together in synch—are at least part of the trigger,” she explains. Cohen is following up on this question by studying religious drummers in Brazil, while her former colleagues continue to experiment with the Oxford rowing crew.

Endorphins are produced by virtually any vigorous physical activity, as confirmed by the fact that even the solo rowing sessions in Cohen’s study enhanced pain threshold to some degree. But group work appears to enhance the effect dramatically—and there’s plenty of evidence that exercise classes meet that description. In a series of studies stretching back more than a decade, University of Saskatchewan professor Kevin Spink has found those who feel a greater sense of “groupness” and cohesion within an exercise class are more punctual, have better attendance, and even work harder.

Of course, not all collections of individuals qualify as a group. Spink and other researchers have identified factors that make some crowds “groupier” than others, such as the existence of group norms. For example, the shift in the past decade from sign-up exercise classes to drop-in classes has made it more difficult to build cohesion in these groups. Still, it appears that the most important factor is what’s in your head, even for drop-in classes. “As long as I perceive the people I’m exercising with as a group, my adherence is way better,” Spink says.

There is an important caveat regarding individual preferences. About a third of people enjoy exercising in groups; another third prefer exercising alone, while the remaining third are indifferent, Spink notes. For those who are happy exercising alone, there’s no reason to join a group. For everyone else, exercising with partners or in groups has all sorts of benefits that have nothing to do with neuroscience, from the simple act of committing to meet someone to the pleasures of gossiping during a workout. But the endorphin findings help explain how exercise is transformed from a chore to a lifelong habit, and indeed a pleasure, for some people—and suggest one way of getting there.

What are the effects of exercise on the brain?

The theme of much of the research described in this post is how much influence your brain has on the way you exercise. But it works the other way around too: the exercise you do has wide-ranging effects on your brain, with the power to alter mood, memory, and even the structure of the brain itself. Over the long term, there’s not much doubt that exercise makes you smarter. Studies in rodents have shown that physical activity makes brains develop denser and more complex connections between neurons and stimulates the growth of new brain cells. These effects are especially important during adolescence and early adulthood, when your central nervous system is developing rapidly and taking the shape it will maintain, more or less, for the rest of your life.

A massive Swedish study published in 2009 combed through the records of 1.2 million 18-year-olds who had taken compulsory military screening exams between 1950 and 1976. The first finding was that aerobic fitness, but not muscular strength, was associated with greater intelligence. But it wasn’t just being fit that helped—getting fit also offered a major boost. Those who had gained the most aerobic fitness from 15 to 18, as assessed from their high school phys ed marks, scored far better on the cognitive tests than those who had lost fitness. Since 268,496 of the subjects were brothers, the researchers were also able to determine that the links between aerobic fitness and intelligence were primarily due to environmental factors like exercise, rather than genetic factors.

The fact that aerobic exercise improves intelligence but strength training doesn’t may come as a surprise. Researchers believe that many of exercise’s neural benefits relate to whole-body effects such as increased blood flow: getting your heart pumping in a cardio workout carries more blood, along with helpful growth factors, to your brain. A 2009 study by University of North Carolina researchers used magnetic resonance angiograms to determine that elderly subjects who did regular aerobic exercise had more small blood vessels in their brains, and fewer twists and turns in those vessels, compared with non-exercising controls. The benefits of strength training, in contrast, tend to be limited to the muscles you’re using.

Although it takes time to rewire your brain, you can tap into some of exercise’s brain-boosting benefits almost instantly. In 2009, researchers at the University of Illinois at Urbana-Champaign put 21 volunteers through a set of tests to assess working memory (the ability to remember something and then retrieve it for use a short time later) immediately after a 30-minute session of either aerobic or resistance exercise, and then repeated the tests half an hour later. The aerobic exercisers improved their reaction time on the post-exercise test and improved it even more on the second test; the strength trainers, on the other hand, were no different from controls who hadn’t exercised at all. These findings apply only to the specific working memory task that was tested, but they suggest that the mental benefits of aerobic exercise start right away.

There are also indications that more (or harder) exercise produces greater cognitive gains. Another 2009 study, from Taiwan’s National Cheng Kung University, found that mice forced to run on a treadmill made greater cognitive gains than mice that ran at leisure on an exercise wheel (though both groups did improve). But there are limits. Extreme exertion like running a marathon generates stress hormone levels comparable to those seen in military interrogations and first-time parachute jumpers, which can interfere with some mental processes. Researchers tested 141 runners immediately after they completed the Boston or New York marathons and found that their “explicit memory,” which answers questions like “What happened an hour ago?,” was impaired. On the other hand, their “implicit memory,” measured by the ability to complete partial words, was enhanced.

New results in this area continue to be published on a regular basis, so it won’t be long before we’re able to say with certainty why the extreme stress of a marathon helps some mental processes and hurts others, or which particular exercise-produced growth factors are key to generating new brain cells. For now, the advice is simple: keep doing all the exercise that’s recommended for a healthy cardiovascular system, and you’ll get a mental edge as a bonus.


• Mental fatigue causes a reduction in physical performance, which suggests that exhaustion is controlled by the brain’s perception of effort rather than the body’s failure.

• The most productive training is “deliberate practice,” which involves setting goals, monitoring progress, and focusing on technique rather than mindlessly repeating drills.

• Responses to music are highly personal, though there are some general patterns (faster music makes you work harder). Watching video is so distracting that it may lead you to slack off.

• Once you’ve mastered skills, whether it’s golf putting or darts, focusing too much on the details can lead to choking.

• Swearing or imagining yourself doing something evil taps into feelings of aggression that enhance physical performance.

• Prolonged physical exercise causes the release of endorphins, which can lead to runner’s high—and exercise addiction.

• Training with a group leads to greater endorphin production, which enhances pleasure and performance. About a third of people prefer working out alone.

• Exercise makes you smarter and improves your memory, starting immediately. Aerobic exercise is more effective than strength training, and the harder the better.

Jean-Paul Marat

Many tips are based on recent research, while others were known in ancient times. But they have all been proven to be effective. So keep this website close at hand and make the advice it offers a part of your daily life.

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